For instance, when a vehicle body of an automobile is manufactured, it is practiced to superpose a plurality of panel parts or the like, which are works, and to perform welding. In this type of welding, the use of a so-called welding gun is conventionally known which has a first electrode tip and a second electrode tip opposing the first electrode tip, whereby a welding target portion of a work is clamped in a pressurized state by the first electrode tip and the second electrode tip, and resistance welding is performed for the welding target portion (e.g., refer to JP-A-11-47944).
However, in a case where an obstacle portion such as a hollow portion is formed on the second electrode tip side of the welding target portion of the work, it is impossible to cause the second electrode tip to directly abut against the opposing side of the welding target portion against which the first electrode tip abuts. Accordingly, in this type of welding guns, one is known which is adapted to be able to move the second electrode tip in a direction of intersecting an opposing axis of the first electrode tip (e.g., refer to JP-A-6-155037). As a result, the second electrode tip can be abutted against the work by being offset from the position opposing the first electrode tip. Even if an obstacle portion such as a hollow portion is formed on the second electrode tip side of the welding target portion of the work, it is possible to ensure electrical conduction between the first electrode tip and the second electrode tip while avoiding the obstacle portion, so that it is possible to perform resistance welding to the welding target portion of the work against which the first electrode tip abuts.
However, in order to cause the second electrode tip to abut against the work by being offset from the position opposing the first electrode tip, the welding gun must be provided with an arrangement for moving the second electrode tip in the direction of intersecting the opposing axis of the first electrode tip. Namely, there are drawbacks in that not only does the construction of the welding gun become complex, but it becomes difficult to construct the welding gun compactly.